High-resolution retinal imaging can significantly improve the quality of diagnosis, disease progression tracking and assessment of therapy in a broad range of retinal diseases including, for example, retinal degenerations (retinitis pigmentosa), macular telangiectasis, macular dystrophies, age-related macular degeneration (AMD), and inflammatory diseases. Some of these diseases are prevalent (AMD afflicts 12% of the population aged 80+, and retinitis pigmentosa is the most common cause of blindness/low-vision in adults 20-60 years old) and progress slowly, which drives the need for a cost-effective imaging solution that can be broadly deployed for screening and tracking purposes. The availability of new therapeutics further drives this need for a cost-effective imaging solution since the ability to discern the exact impact of the drugs at the cell level is highly useful in informing clinicians about the course of treatments.
Accounting for the numerical aperture of the eye as set by a nominal pupil diameter of 6 mm, an imaging system should be able to focus light to a diffraction-limited spot of size of 1.9 microns on the retina (630 nm wavelength) except that aberrations in the eye actually result in a much poorer focus spot. Conventional retinal imaging techniques correct for aberrations by including a corrective physical optical arrangement to compensate for the aberrations before acquiring images. This conventional strategy is the basis of the adaptive optics (AO) work that was first started in astronomy and that has been applied to ophthalmic imaging systems, in particular confocal scanning laser ophthalmoscopes (cSLO). Conventional adaptive optics scanning laser ophthalmoscopes (AOSLO) have significant limitations that have hindered their broad clinical use. First, the field of view of AO corrected images tends to be very small oftentimes only 1 degree in size. Since retinal diseases can occupy large portions of the macula and retina, conventional AO techniques requires multiple images to be obtained and montaged and increases the acquisition time. Long acquisition times are generally impractical for routine clinical use, especially with eye motion from the patient. This requires high-speed tracking systems since AO requires feedback to keep the aberration correction current. Second, the uneven topology of many retinal diseases presents a major challenge because regions not in the focal plane of the optics will appear out of focus. Third, despite reductions in the cost of certain components, such as deformable mirrors, these conventional systems still remain expensive, limiting their commercial feasibility.